THE EFFECT OF TEMPERATURE UPON FACET 



NUMBER IN THE BAR-EYED MUTANT OF 



DROSOPHH^A* 



Part II. NEW roi^ 



By JOSEPH KRAFKA, Jr. ■'<*TANfCAI. 



{From the Zoological Laboratory of the University of Illinois, Urbana.) 

 (Received for publication, December 30, 1919.) 



Determination of the Period during Which Temperature is Effective in 

 Modifying the Facet Number. 



Preliminary Experiments on Unselected Bar Stock at 30 and 15°. 



A preliminary experiment was planned to determine whether tem- 

 perature had an effect throughout the immature stages or whether 

 it was limited to a specific phase of development. In Table XIV^ are 

 shown the results of subjecting successive cultures for the 1st day, 

 first 2 days, first 3 days, and so on to 30° before subsequent devel- 

 opment at 15°. 3, 2, and 1 days at 30° give the same facet number 

 as those raised at 15° throughout. The early days of larval life 

 may be spent at high temperatures without effect on the facet number, 



6 and 7 days at 30° followed by transfer to 15° show that the 

 number of facets had been determined prior to the transfer, as indi- 

 cated by the fact that all the counts come well within the range of 

 the stock counts at 30°. 



Next, if we consider only those counts made on the 1st day of 

 hatching, the bottles that were kept at 30° for the first 4 and 5 days 

 show only the facet counts characteristic of the 30° stocks. The 

 counts made on the flies hatching on the 2nd and 3rd days are inter- 



J * Contribution from the Zoological Laboratory of the University of Illinois, 



- No. 148. 



^ * Krafka, J., Jr., /. Gen. Physiol, 1919-20, ii, 409. 



433 



